Eco-evolutionary feedbacks promotes species coexistence in the fig-wasp mutualism with Allee effect

Mutualistic relationships between species have always fascinated ecologists because of the key role they play in ecosystem functioning. Early studies on the mutualism focused on the mutual influences and constraints between mutualistic parties and the environment. In fact, ecological and evolutionary processes may occur at the same time scale, which means that the coupling of these two processes needs to be fully considered. However, it is still a lack of coupled population dynamics and phenotypic trait dynamics of species to explore maintenance mechanisms of the mutualism. Here, we developed an eco-evolutionary model to investigate intrinsic driving forces for the maintenance of fig-wasp mutualism by coupling population dynamics, phenotypic trait (i.e., style and ovipositor) evolution, and Allee effect of the fig tree. Theoretical results found that: (i) the presence of the Allee effect contributes to the stabilisation of mutualistic relationships in the fig-wasp system; (ii) the fig-wasp mutualism is more prone to oscillation when the evolutionary rate of the style is greater than that of the ovipositor, and population dynamics of mutualistic parties are mainly dominated by interspecific interactions; (iii) under a relatively harsh environment, the eco-evolutionary model predicts the coexistence of species, whereas the ecological model does not. Our work suggests that eco-evolutionary feedbacks have an important effect on the stability of ecosystems, with a view to providing theoretical support for the understanding of interspecific interactions in general mutualistic systems and for the conservation of biodiversity.